<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width">
  <!-- width => 布局视口    device-width => 设备独立像素 -->
  <title>理想视口</title>
  <link rel="stylesheet" href="../重置样式表/reset.css">
  <style>
    #demo{
      width: 375px;
      height: 200px;
      background-color: crimson;
      color: white;
      font-size: 20px;
    }
  </style>
</head>
<body>
  <div id="demo">123</div>
  <script type="text/javascript">
    const demo = document.getElementById('demo')
    demo.innerHTML = '布局视口宽度:' + document.documentElement.clientWidth + '</br>'
    demo.innerHTML += '视觉视口宽度:' + window.innerWidth
  </script>
</body>
</html>